/Engine/Source/Editor/AnimGraph/Public/AnimGraphNodeAlphaOptions.h
This is implemented in this way (rather than encapsulating the options in their own struct) because we dont support exposing pins from sub-structs on anim nodes (or anything else for that matter).
template<typename AnimNodeType> static void HandleCustomizePinData ( const AnimNodeType & InAnimNode, [UEdGraphPin](API\Runtime\Engine\EdGraph\UEdGraphPin) * InPin )